Bulk Lecithin is a multifunctional cosmetic ingredient and active substance. Its purpose of action depends on the properties (flexibility/rigidity) it acquires at skin temperature. They both penetrate deep into the skin to enhance transport and support the skin's barrier function. Lecithins are of great interest in natural cosmetics. Certain categories have been certified non-GMO and evaluated as truly natural by COSMOS, an authoritative international natural certification body. The following is an introduction to using lecithin as an active agent in cosmetic formulations.
Lecithin In Cosmetics
The lecithin bulk powder commonly used in cosmetics is saturated lecithin.
It has better stability and lower iodine value after hydrogenation. It is not easily oxidised and can effectively decolourise and deodorise. It also enhances emulsification for a better skin feel.
1. Repairing the skin barrier
The skin barrier is the stratum corneum of the skin. Without the stratum corneum, the body loses about 20 litres of water daily. Formulations containing saturated soya PC have skin-protective properties. They restore and stabilise the skin's barrier layer. Trans-epidermal water loss (TEWL) measurements have shown that formulas containing saturated soy PC can repair dry, irritated skin to its natural TEWL levels. The layered structure of the formula closely resembles the structure of the skin. It mimics the skin's layered structure and integrates seamlessly into the skin barrier, reducing voids. This will reduce moisture loss and repair the skin barrier.
2. Moisturising
Bulk Lecithin is hygroscopic and binds water molecules. This acts as a moisturiser and increases the hydration level of the skin. In general, dry lecithin can absorb up to 12% of water. This means that approximately 5 water molecules will bind to one lecithin molecule. If lecithin is fully hydrated in the form of liposomes, each lecithin molecule can bind up to 20 water molecules.
Metabolites of lecithin also have good moisturising properties. In the skin, the metabolites of lecithinylcholine are choline, betaine, and glycerophosphorylcholine (GPC). These metabolites are known as osmoprotectants that attract water molecules and act as moisturisers.
An experiment investigated the effect of soybean PC on skin moisture at different concentrations. Liposome dispersions containing 0% (0.9% NaCl control), and three 10% (w/w) were used on 10 volunteers. Which used lecithin with different PC content to 10 volunteers. 10%, 28% and 80%, respectively. The results of the experiments showed that for the liposome made with 80% soybean PC the amount of liposomes used was 10% (w/w), and there was a significant increase in skin moisture. A weaker effect was shown for liposomes made from 28% soybean PC at a dosage of 10% (w/w). Whereas the liposomes made with 10% soy PC at a dosage of 10% (w/w) showed a decrease in skin moisture. The only difference between these formulations was the different soybean PC content. Therefore, it can be concluded that the high content of soybean PC has a moisturising effect on the stratum corneum.
3. Improvement of skin roughness
An experiment was conducted to study the effect of bulk soy Lecithin in formulations on skin roughness. By comparing 20 volunteers' repeated topical application of a liposomal aqueous dispersion containing 20.6% bulk lecithin (purity 93%) with an oil-in-water emulsion containing about 16% ethanol, respectively. It was demonstrated that the roughness of the skin was significantly reduced with the soy PC-containing formulation.
4. Improvement of skin inflammation
Unsaturated diacyl lecithin will serve as a source of linoleic and linolenic acids for the skin. Lecithin-containing linoleic acid reaches the part of metabolically active skin cells and may enhance the skin's natural barrier function by binding with skin ceramides to effectively protect against the irritation of external pollutants. Meanwhile, linolenic acid bound to lecithinylcholine may eventually be converted to some extent into omega-3 fatty acids, docosahexaenoic acid (DHA, 22:6n-3) and eicosapentaenoic acid (EPA, 20:5n-3). These lecithins can play a role in inhibiting acne, neurodermatitis and psoriasis.
Lecithin Functions
Lecithins are surface active due to their amphiphilic (hydrophilic and lipophilic) structure. They are used in cosmetic formulation technology as emulsifiers, liposome/laminar formers, solubilising agents or wetting agents.
1. Emulsifiers
Diacyl lecithins are considered to be very mild surfactants and excellent emulsifiers. The cylindrical diacyl lecithin molecules hydrate to form a lamellar structure or liposomes, so they cannot form droplets spontaneously, and mechanical energy is required to disrupt the structure of the liposomes, forcing the lecithin molecules to position themselves at the oil-water interface. This results in very stable oil-in-water or water-in-oil emulsions/creams. Diacyl lecithin emulsifiers are both soluble in the oil phase and dispersible in the water phase. Lecithin has a wide range of chemical structures and polarities. Bulk lecithin has different emulsifying abilities for different oil phases and can be used as the sole emulsifier in natural cosmetics.
2. Liposome/laminar structure
Lecithins have a unique characteristic compared to other emulsifiers. They can form closed vesicle structures called liposomes upon hydration. It consists of a bilayer of lecithin surrounding an aqueous inner core. Liposomes are similar to the basic structure of natural cell membranes. Both contain bilayer lecithin molecules that act as a membrane protein matrix. This makes liposomes biocompatible. Two major factors affect the permeability of liposomes.
• Particle size:
Common types of liposomes are small unilamellar vesicles (SUVs) with a particle size of 100 nm, large unilamellar vesicles (LUVs) with a particle size of 100-500 nm, and multilamellar vesicles (MLVs) with a particle size of 500 nm to a few microns. For cosmetic applications, large monolayer vesicles are the most common. This is because the degree of encapsulation of water-soluble compounds is influenced by the morphology and size of the liposomes. Large unilamellar vesicles have a large enough volume of encapsulated aqueous solution to effectively encapsulate water-soluble compounds. These liposomes are readily fabricated in a range of sizes that enable good skin interactions.
• Lipid composition:
Liposomes become either deep skin penetrants or skin protectants. Lipid composition plays a decisive role. Liposomes of saturated lecithin have a phase transition temperature of 40-60°C. At a skin temperature of 32°C, the liposome has a rigid structure. It does not penetrate significantly into the skin. It acts more as a protective, skin-compatible barrier layer. Unsaturated lecithin has a liposome phase transition temperature of less than 0°C. At skin temperatures, the liposome is flexible and mobile and can penetrate deeply into the skin. Thus, unsaturated lecithins are suitable as penetration enhancers/transport carriers that can carry their encapsulated compounds deeper into deeper layers of the skin. In addition, they help to maintain or restore the healthy condition of the skin by supplying a wide range of unsaturated fatty acids. On the other hand, bulk lecithin is beneficial in maintaining or restoring skin health by physically stabilising the skin barrier.
3. Solubilising agents
Bulk lecithin acts as a solubiliser in various cosmetic formulations. They are used as emulsifiers in oil-in-water microemulsions with an oil droplet size of about 50 nm. The oil phase can be the formulator's favourite oil. They are either used as a solubilising phase together with lecithin at the oil-water interface to solubilise other (oil-soluble) lipophilic ingredients. such as plant extracts. In addition, lecithins can be used in mixed micelles comprising mono- and diacyl lecithins or diacyl lecithin analogues. combined with another surfactant to solubilise the lipophilic compounds. The lipophilic portion of the liposome bilayer membrane can also solubilise some compounds. Several transparent lecithin bulk concentrates can be used as solubilising agents in oily excipients.
4. Wetting agents
Due to its amphiphilic nature, lecithin is an excellent wetting agent for dispersing lipophilic compounds. For example, pigments in hydrophilic media.
The choice of which lecithin to use should be based on the specific needs of the product. Factors such as emulsification performance, cost, and source of ingredients are considered. Guanjie Biotech is a professional bulk lecithin manufacturer and supplier, welcome to enquiry us: info@gybiotech.com.
